Precipitated silicas, silica gels with and free of deposited carbon from caustic biomass ash solutions and processes

Abstract

Disclosed are amorphous precipitated silicas, silica gels, and amorphous carbons derived from biomass and methods of producing them with and without adhered or deposited amorphous carbons produced by acidifying a caustic silicate solution produced by caustic digestion of biomass ash containing silica with and without activated carbon, the ash being obtained from thermal pyrolysis of the biomass, the acidifying effective to produce a slurry of the precipitated silica and silica gels with and without adhered or deposited amorphous carbon, and separated from the slurry the precipitated silicas and silica gels with and without the adhered or deposited amorphous carbons. The properties of the precipitated silica with adhered or deposited carbon being within the range as utilized in rubber compositions thereby avoiding the blending of silica and carbon components for such use. The precipitated silicas and silica gels without adhered or deposited carbon having metal contaminants present in low concentrations which when used in formulation of chemical-mechanical-planerization slurries used in polishing silicon wafers in the manufacture of computer chips and other electronic devices do not contaminate the wafer and final chip product and the other electronic devices.

What is claimed is:  
     
       1. A method of producing amorphous precipitated silicas or silica gels, wherein each silica has adhered or deposited amorphous carbons thereon comprising, 
       acidifying a caustic silicate solution produced by caustic digestion of biomass ash containing silica and activated carbon, the ash being obtained from thermal pyrolysis of the biomass, the acidifying being effective to produce a slurry of the precipitated silica or silica gels, and  
       separating from the slurry, the precipitated silicas or silica gels with the adhered or deposited amorphous carbons.  
     
     
       2. The method of  claim 1  where, 
       the biomass ash comprises rice hull ash.  
     
     
       3. The method of  claim 1  where, 
       the acidifying is by an acid selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, acetic acid, and combinations thereof.  
     
     
       4. A method of producing amorphous precipitated silicas or silica gels comprising, 
       acidifying a caustic silicate solution produced by caustic digestion of biomass ash containing silica and being free of activated carbon, the ash being obtained from thermal pyrolysis of the biomass,  
       the acidifying being effective to produce a slurry of the precipitated silica or silica gels, and  
       separating from the slurry the precipitated silicas or silica gels.  
     
     
       5. The method of  claim 4  where, 
       the biomass ash is rice hull ash.  
     
     
       6. The method of  claim 4  where, 
       the acidifying is by an acid selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, acetic acid, and combinations thereof.